Trawling involves the deployment of a funnel shaped trawl net from a fishing vessel in the ocean to harvest marine organisms. The trawl net is suspended horizontally between opposite side paravane members (trawl boards), which cause the trawl net to assume a position suitable for fishing. The outward pitch of the opposite side paravane members relative to the towing force of the vessel, causes a hydraulic pressure that creates a substantial outward lateral force on the sides of the trawl net. This force holds the trawl net open and close to the sea bottom.
Typically, the constructions of trawl nets require a tubular, funnel-shaped section of net material, known as the trawl body. Lining the opening of the trawl body is a reinforcing rope, which also attaches the trawl net of the trawl doors. The upper reinforcing rope of the trawl is the headrope. This rope limits the outward lateral movement of the trawl boards. The limiting force of the headrope, combined with the hydraulic resistance of the trawl, causes the trawl to assume a horseshoe shape when viewed from the top. Furthermore, multiple floats lift the headrope and weights hold down the lower boundary rope, or footrope. These features serve to further spread open the mouth or collection portion of the trawl. Boundary ropes on either side of the trawl, or side ropes, connect the headrope with the footrope and reinforce the forward end of the trawl side panels.
At the central aft end of the trawl body, connects another tubular net section known as an extension. Connecting to the extension is a terminal tubular net section known as the cod-end or tailbag. The tailbag is of substantial construction and constricting lines restrain the tailbag opening, confining the catch while the trawl net is in operation.
The body of the trawl net serves to collect and guide objects and organisms, unable to avoid capture, through the extension into the tailbag. The extension adds length to the trawl net, adding significant handling characteristics to the retrieval and emptying of the tailbag while towing trawl nets "double-rigged" or with one trawl net on each side of the fishing vessel.
In fishing for a small crustacean, shrimp, for example, the mesh of the trawl net is typically small. Because a trawl net filters a substantial swath of the ocean, significant other objects and organisms are captured while trawling. These objects and organisms are either useless to the fisherman or protected by public law. For example, marine reptiles, such as sea turtles, are easily captured because they are unable to swim against the flow produced by the trawl towing speed. The National Marine Fisheries Service, a branch of the United States Government, has developed regulations (50 C.F.R. 217, 222 and 227) governing the use of trawl nets without certified turtle excluder devices (TED's). Said regulations significantly limit tow times for trawl nets not equipped with TED's. The increased need for retrieval and redeployment of the trawl net to release captured turtles increases the expense and labor of the fisherman. Besides this, trawl nets capture unwanted organisms, trash, litter, and other inanimate objects during the trawling operation. A trawl net device or apparatus providing the function of separating and excluding objects and other organism from the targeted species is of a necessity to fishermen using fishing trawls.
Such a trawl net device must positively exclude legally protected species, such as sea turtles, and simultaneously, fisherman must understand and safely handle the device. Preferably, the trawl net device should be constructed of soft, commercially available fabric or netting material. The trawl net device should not provide for openings in the collection areas through which the target species could escape.
Prior art includes metal and/or hard plastic devices installed in the collection areas of trawl nets. Such devices usually provide for an angled barrier of parallel bars that cause large objects and organisms to be forced upward or downward through a flap, door or other opening. Simultaneously, large amounts of the target species escape with the object or organism as it exits through the opening. Similar other devices substitute net webbing for the metal or plastic angled bars. In 50 CFR 22.772 (4) (ii) (G.) of the Federal Register (Vol. 55, No. 195, Tuesday, Oct. 9, 1990, Page 41090 and 41091), the Andrews TED uses a fabric barrier and provides an opening forward of the trawl extension. However, significant amounts of the target species escape through the unprotected opening in the outer trawl fabric.
Other devices are designed to exclude fish or other organisms with superior swimming ability. These devices provide for an opening in the top, side or bottom of the extension or tailbag portions of the trawl. Fish or other organisms escape, due to hydraulic variations produced by these devices in the trawling stream flow. Again, unprotected openings in the collection areas of the trawl, allow escape of the target species.